1. Field of the Invention
The present invention relates to a novel temperature sensitive plasmid for coryneform bacteria. This plasmid can be utilized for modifying a chromosomal gene of coryneform bacteria, which are used for the production of useful substances such as amino acids by fermentation, to change their genetic traits. Thus, the plasmid can be utilized for breeding of microorganisms useful for the production of amino acids by fermentation and so forth.
2. Related Art
There has already been reported an attempt to alter a genetic trait of coryneform bacteria by intentionally modifying a particular gene on their chromosomes, or by stably incorporating a gene of a defined copy number into the chromosomes, thereby utilizing such coryneform bacteria for the production of useful substances such as amino acids by fermentation [Japanese Patent Publication Laid-open (Kokai) No. 5-7491]. This utilizes a plasmid in which a replication control region of the plasmid DNA enabling autonomous replication of the plasmid is modified to be a replication control region having temperature sensitive mutation, which makes the replication impossible when the culture temperature is elevated. However, when such a plasmid containing a temperature sensitive replication control region is used in coryneform bacteria harboring another plasmid having a wild-type replication control region from which the temperature sensitive replication control region has been derived, homologous recombination may be caused between the plasmids. Thus, a phenomenon that the plasmid harbored by the transformant no longer has the temperature sensitive replication control region has been observed. Similarly, when it is intended to modify a gene on a chromosome of coryneform bacteria using such a plasmid, a phenomenon that this plasmid is eliminated due to incompatibility in the process of breeding has also been observed if a host coryneform bacterium harbors a plasmid which has a replication control region of the same origin as the aforementioned plasmid.